Tests such as lateral flow tests which measure colour or pattern variation of at least two lines in a test strip are read with manufacturer-specific readers, but more generic apparatuses are currently emerging. As an example, a portable mobile consumer electric device is described in WO 2012/131386.
When a portable camera is used for capturing an image of a test strip, the lighting condition varies a lot due to many reasons such as: an angle of view may be different for different captures; angle of illumination is usually different for different captures; a camera can cover and shadow a part of the test strip when capturing an image; a camera user can obscure or shadow a part of the test strip during capturing an image; intensity of a flash of the portable camera is stronger at one side than at another side of the imaged area; due to the angle variations illumination from a light source such as flash or from the sun may cause severe over-exposure or under-exposure in some parts of area imaged.
This variation causes the lines in the test strip to be differently illuminated and differently detected by the portable camera. For example, a test strip can be imaged in various directions: left to right, right to left, upside down or downside up. An accurate control of illumination cannot be arranged because an image of the area indicating test result is captured without a standardized test box.
As the test reader is used by a lateral flow assay test user, who is probably not an expert in taking pictures, all other kinds of variations such as tremble of hands, occasional operational errors and many other disturbances may cause failure in capturing the image, quality deterioration or quality loss in the image.
Hence, there is need for improvement in the ratiometric measurements made by a portable camera.